Various polymer and resin mixtures have been proposed for adhesives with strong bonding properties for various substrates and these have been successful to varying degrees. However, the blends of this invention have remarkably superior properties when used as adhesives. Thus the object of this invention is to provide modified polyolefin resins with improved adhesion to substrates such as polar polymers, metals, glass, paper, wood, etc. These resins can be applied in any conventional manner and typical application processes are lamination, extrusion coating, coextrusion, powder coating, blow molding, etc.
It is well known that laminates of polyolefins with dissimilar substrates have many desirable characteristics. Among these are heat sealability and barrier properties. However, it is often difficult to bond polyolefins to dissimilar substrates because of the differences in physical and chemical structures. To overcome the bonding difficulties, it has been proposed in the past to use either an adhesive layer between the polyolefin and the substrate or a more expensive, highly polar copolymer of the olefin such as an ionomer resin in place of the conventional polyolefin. This latter is not entirely successful because, although the ionomer resin may show good adhesion, the bond formed is easily weakened by exposure to moisture or common solvents.
Another method for improving the adhesion of a polyolefin to a substrate is to graft polar functional groups onto the polyolefin backbone chain. The most common combination is maleic anhydride grafted to polypropylene. However, grafting of maleic anhydride on a polyethylene backbone when applied as in this invention does not give the adhesive power of the products of this invention.